Dynamic matched filter bank and its application in multi-channel spread spectrum communication systems

ABSTRACT

A dynamic matched filter bank consists of a plurality of matched filters with either the reference signal for each matched filter changes with the time or the input signal to a matched filter is the received signal modified by a different way for a different matched filter. A receiver employed a set of dynamic matched filter banks in a multi-channel spread spectrum communication system consists of a signal register, a block PN generator, a plurality of spreading sequence generators, a plurality of register arrays, a plurality of multiplier arrays, a plurality of matched filters, a plurality of signal combiners, and a controller. The block PN generator generates a section of PN sequence at the end of every symbol period with feedback logic to shift a block of chips each time. A register array captures each section of PN sequence from the block PN generator and delays it for a symbol period. The rest register arrays are in cascade and delay the section of sequence at each of their inputs by one symbol period. The signal register generates a moving section of the received signal. Each of the multiplier arrays multiplies each moving section of the received signal by a section of PN sequence from either the block PN generator or one of the register arrays to provide a input signal to a corresponding matched filter. Each of the matched filter is to find the correlation between the section of its input signal and the section of its reference signal, which is a spreading sequence from a corresponding spreading sequence generator. Each of the signal combiners will combine the components from corresponding matched filters. The controller will monitor the signals from all matched filters and all signal combiners, extract necessary information, and generate various control signals.

FEDERALLY SPONSORED RESEARCH

[0001] Not Applicable

SEQUENCE LISTING OR PROGRAM

[0002] Not Applicable

FIELD OF THE INVENTION

[0003] The invention is generally related to a bank of matched filtersemployed in a communication circuit. More particularly the invention isrelated to a bank of matched filters for detecting, tracking, andcombining the components of a multipath signal spanned over severalsymbol periods in a radio link of a multi-channel direct sequencespreading spectrum communication system.

BACKGROUND OF THE INVENTION

[0004] In a wireless communication system, especially in a mobilecommunication system, fading occurs from times to times. Buildings,mountains, and foliage on the transmission path between a transmitterand a receiver can cause reflection, diffraction, and scattering on apropagating electromagnetic wave. The electromagnetic waves reflectedfrom various large objects, travel along different paths of varyinglengths. If there is an obstacle with sharp irregularities on thetransmission path, the secondary waves resulting from the obstructingsurface are present around the obstacle. Also if there are smallobjects, rough surfaces, and other irregularities on the transmissionpath, scattered waves are created. All these waves will interact witheach other and cause multipath fading at specific locations.

[0005] The multipath fading can seriously deteriorate the quality of acommunication system. In a multi-channel communication system, themultipath fading could be more serious. Each component of a multipathfading signal on a particular channel only not interferes with the othercomponents of the signal, but also interferes with each component of thesignals on other channels.

[0006] Direct sequence spread spectrum system is multipath resistant dueto the fact that the delayed versions of the transmitted pseudo-noise(PN) signal have poor correlation with the original PN signal. Togetherwith a RAKE receiver, a direct sequence spread spectrum system cancombine the information obtained from several resolvable multipathcomponents and therefore improve the system performance.

[0007] In a RAKE receiver, usually there are a searcher, severalfingers, and a signal combiner. A searcher is a device to detect eachmajor component of a multipath signal and obtain the information aboutthe component, such as signal strength, phase, and time relation. Afinger is a device to track a particular component of a multipathsignal. A signal combiner is a device to combine the various componentsof a multipath signal together.

[0008] One can build a searcher based on either correlator or matchedfilter. A searcher based on correlator shifts its local reference signalby an amount of time and then compares the input signal with the shiftedlocal reference signal for a period of time. It finds the multipathinformation by repeating the process of shifting and comparing. Usually,the smaller the amount of time shifted, the higher the time resolutionon a multipath signal; the longer the period of time compared, the morereliable the detection result. A searcher based on matched filtercompares a fixed section of reference signal with a section of inputsignal while the input signal keeps coming. The lengths of both sectionsare equal. It can detect a component of a multipath signal immediatelywhen the component is coming. Generally speaking, to have about the sameconfidence on detection result, a searcher based on correlator needsless hardware but more time, while a searcher based on matched filterneeds less time but more hardware.

[0009] In a packet-switched communication system, the packet receivedcould come from total different source than the previous one andgenerally there is no any relation between two adjacent packets. Inorder to obtain multipath information quickly, one may desire to usematched filter especially when transmission rate is very high. Also eventhere are some similarities between a searcher and a finger, in manycommunication systems, searchers and fingers are built separately, whichresults in more hardware. In order to save hardware, one may desire touse the same set of matched filters to serve both searcher and fingers.

[0010] A portion of a searcher based on regular matched filter is shownin FIG. 1.

[0011] The signal register 105 consists of a plurality of registers withthe first register connected to input signal S_(in) and each of the restregisters connected to its previous one. Usually these registers aredriven by a same clock such as the sampling clock of input signalS_(in). There is a tapped output after every several registers andtogether there are M tapped outputs. The signals at the M outputs arereplicas of the input signal S_(in) with different delays. The delaybetween any two adjacent output signals is the same.

[0012] The fixed reference signal 110 also has M output signalsinvariant with the time. They are a sampled version of a local referencesignal in a predetermined time interval with the delay between any twoadjacent samples being equal to the delay between two adjacent outputsignals of signal register 105. When the local reference signal is a PNsequence, the fixed reference signal is a section of the PN sequence.

[0013] A section of input signal S_(in) is represented by M outputsignals from signal register 105 and a section of the local referencesignal is represented by M output signals from fixed reference signal110.

[0014] The matched filter 115 consists of a plurality of multipliers andan adder. Each of the multipliers 120 ₁ to 120 _(M) will multiply anoutput signal from fixed reference signal 110 with a correspondingoutput signal from signal register 105. The adder 125 will add theproducts from all of the multipliers together. Matched filter 115 takesthe summation as its output, which is the correlation between thesection of input signal S_(in) and the section of the reference signal.

[0015] Since FIG. 1 is part of a searcher, it is desirable that eitherthe M signals from local fixed reference signal 110 correspond to aunique word specially for finding various components of a multipathsignal or M is very large so that there is no confusion to identify amultipath component. To save hardware, one may want to use the samehardware to serve a finger. As FIG. 1 has to be part of a finger, the Moutput signals from local fixed reference signal 110 can not be the sameunique word required by searcher, otherwise the word is not unique.Also, the M output signals should correspond to one symbol periodotherwise it is difficult to separate the contribution of the first datasymbol from the contribution of the second data symbol. However, whenthe M output signals from local fixed reference signal 110 correspond toone symbol period and do not correspond to a unique word, the searcherbased FIG. 1 can not detect a multipath signal spanned over severalsymbol periods. Because there is no way to tell that if a detectedcomponent is a component of first symbol or a component of secondsymbol.

[0016] To detect and track a multipath signal spanned over more than 1symbol period correctly based on a same set of matched filters, it isnecessary for the reference signal to be different in several adjacentsymbol periods. In regular matched filter, the reference signal is fixedas shown in FIG. 1. Therefore when the reference signal varies fromsymbol period to symbol period, the structure based FIG. 1 does notapply. To distinguish from regular matched filter, one can refer amatched filter with a variable reference signal or with a modified inputsignal as a dynamic matched filter.

[0017] It would, therefore, be desirable to build dynamic matchedfilters in a receiver for detecting, tracking, and combining the variouscomponents of a multipath signal spanned over several symbol periods.

OBJECTIVES OF THE INVENTION

[0018] The primary objective of the invention is to detect, track, andcombine the various components of a multipath signal based on a same setof dynamic matched filters.

[0019] Another objective of the invention is to construct a receiverbased on a set of dynamic matched filters with the capability to detect,track, and combine the various components of a multipath signal scattedover several symbol periods on each channel of a multi-channelcommunication system.

[0020] Another objective of the invention is to reduce the totalhardware needed for building individual searcher and finger by jointlydesigning a set of dynamic matched filters in a receiver of amulti-channel spread spectrum communication system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in andconstitute a part of the specification, depict the preferred embodimentsof the present invention, and together with the description, serve toexplain the principle of the invention. In the figures, like referencenumerals refer to the same or similar elements.

[0022]FIG. 1 illustrates a portion of a searcher subsystem based onregular matched filter.

[0023]FIG. 2 illustrates the first embodiment of a dynamic matchedfilter bank in a direct sequence spread spectrum communication systemwith the reference signal consisting of a spreading signal and ascrambled signal.

[0024]FIG. 3 illustrates the second embodiment of a dynamic matchedfilter bank in a communication system.

[0025]FIG. 4 illustrates the third embodiment of a dynamic matchedfilter bank in a direct sequence spread spectrum communication systemwith the reference signal consisting of a spreading signal and ascrambled signal.

[0026]FIG. 5 illustrates the fourth embodiment of a dynamic matchedfilter bank in a communication system.

[0027]FIG. 6 illustrates spreading signals for each of themulti-channels and a scrambled signal of a multi-channel direct sequencespread spectrum communication system.

[0028]FIG. 7 illustrates the essential of a transmitter in amulti-channel direct sequence spread spectrum communication system withthe spreading signals and the scrambled signal as in FIG. 6.

[0029]FIG. 8 illustrates the essential of a receiver with a set ofdynamic matched filter banks in a multi-channel direct sequence spreadspectrum communication system with a reference signal consisting of thespreading signals and the scrambled signal as in FIG. 6.

[0030]FIG. 9 illustrates the essential of another receiver with a set ofdynamic matched filters in a multi-channel direct sequence spreadspectrum communication system with a reference signal consisting of thespreading signals and the scrambled signal as in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Detailed description of the preferred embodiments is providedherein. The embodiments illustrate dynamic matched filter bank and itsapplications in communication systems by way of examples, not by way oflimitations. It is to be understood that it could be easy for thoseskilled in the art to modify the embodiments in many different ways.

[0032] For example, instead of first mapping a binary bit into +1 or −1value, then multiplying a signal by value +1 or −1 correspondingly, onecan let the signal pass when the binary bit is 0 and let the negative ofthe signal pass when the binary bit is 1.

[0033] Here is another example. Instead of multiplying or exclusive-oreach chip of a binary PN sequence by the corresponding chip of a binaryspreading sequence, one can design linear feedback shift register withsuch a feedback logic that the generated sequence is the exclusive-or ofthe PN sequence and the spreading sequence.

[0034] More complex example could be given. In FIG. 8, first a sectionof a modified input signal is obtained by multiplying a section ofreceived signal with a section of a scrambled signal. Then a matchedfilter is used to find the correlation between the section of themodified input signal and a section of a spreading signal. Instead, onecan obtain a section of a modified input signal by multiply a section ofreceived signal with a section of a spreading signal, and then let amatched filter to find the correlation between the section of themodified input signal and a section of a scrambled signal.

[0035] Therefore, specific details disclosed are not to be interpretedas limitations, but rather as bases for the claims and as representativebases for teaching one to employ the present invention in virtually anyappropriately detailed system, structure or manner.

[0036]FIG. 2 shows the first embodiment of a dynamic matched filter bankin a direct sequence spread spectrum communication system with thereference signal consisting of a spreading signal and a scrambledsignal.

[0037] There are several assumptions. First, the local reference signalconsists of a spreading signal and a scrambled signal. Second, themultipath fading spans over less than L symbol periods. Third, the Moutput signals from either signal register or block scrambled signalgenerator correspond to a symbol period. Fourth, the spreading signalhas only one section, which corresponds to a symbol period and does notchange with the time. Fifth, the section of a scrambled signal in anysymbol period is different from the section in any other adjacent Lsymbol periods.

[0038] The reference signal is a combination of a scrambled signal and aspreading signal. In FIG. 2, a plurality of modified input signals areobtained by modifying the input signal with the scrambled signal withdifferent delays. And a bank of matched filters are used to obtain thecorrelation values between each of the modified input signals and thespreading signal.

[0039] The signal register 205 has M tapped output signals. These Mtapped output signals could be simply plural copies of the input signalS_(in) with the delay between any two adjacent copies being the same. Insome cases, the M tapped output signals could be a moving section ofsampled version or an interpolated version of the input signal.

[0040] The block scrambled signal generator 210 generates M outputsignals. These M signals are a sampled version of a scrambled signal ina symbol period. For the scrambled signal changes with the time, these Msignals also change from one symbol period to another but are constantduring any symbol period. When the scrambled signal is a PN sequence, ablock scrambled signal generator is a block PN generator and a block ofscrambled signal is a window of M chips of a PN sequence with the windowmoving M chips at the end of every M chip clocks or one symbol period.One can build a linear feedback shift register as the block scrambledsignal generator 210 with the feedback logic to shift M chips at the endof every M chip clocks. Of course, when the PN generator has less than Mstages, extra registers should be appended so that there are M signalsout of the block scrambled signal generator 210.

[0041] The M signals from block scrambled signal generator 210, areconnected to a multiplier array 225 ₁ and a register array 215 ₂. Eachregister array consists of M memory elements 220 ₁ to 220 _(M) driven bya symbol clock. The register array 215 ₂ is connected to anothermultiplier array 225 ₂ and cascaded by another register array 215 ₃ (notshown in the figure). There are total L−1 register arrays 215 ₂ to 215_(L) in cascade.

[0042] Each M signals from the block scrambled signal generator 210 andthe L−1 register arrays 215 ₂ to 215 _(L) are sent to one of multiplierarrays 225 ₁ to 225 _(L) respectively. In each of the multiplier arrays,there are M multipliers 230 ₁to 230 _(M) Each multiplier multiplies atapped output signal from signal register 205 with a correspondingsignal from the block scrambled signal generator 210 or from one of theregister arrays 215 ₂ to 215 _(L). When the scramble signal is a binarysequence, one can use a selective device instead of a multiplier. Forexample, if binary 0 lets a tapped output signal from signal registerpass, then binary 1 will let the negative of the tapped output signalpass.

[0043] The spreading signal 250 also has M output signals. These Msignals correspond to a symbol period and do not change with the time.

[0044] The M outputs from each of the L multiplier arrays are sent toone of the L matched filters 235 ₁ to 235 _(L). In each matched filter,there are M multipliers and an adder. Each of these multipliers 240 ₁ to240 _(M) multiplies the product from a corresponding multiplier in amultiplier array with a corresponding signal from the spreading signalgenerator 250. When the spreading signal is binary sequence, one can usea selective device instead of a multiplier with binary 0 to select aproduct itself and binary 1 to select the negative of the product.

[0045] The adder 245 in each matched filter will add all the productsfrom the M multipliers in each matched filter together. Each matchedfilter takes a corresponding summation as its output. The outputs fromall these matched filters will be sent to signal combiner 255.

[0046] For a signal consisting of the combination of a spreading signaland a section of a local scrambled signal, the first matched filter 235₁ will detect all of the multipath components of a signal falling intothe first symbol period. The second matched filter 235 ₂ will detect allof the multipath components of the signal falling into the second symbolperiod. The No. L matched filter 235 _(L) will detect all of themultipath components of the signal falling into the No. L symbol period.The L matched filters 235 ₁ to 235 _(L) comprise a matched filter bank.

[0047] The outputs from all matched filters 235 ₁ to 235 _(L) and signalcombiner 255 will be sent to controller 260. The controller 260 willmonitor the signals from each matched filter. It will examine not onlyvarious multipath components, but also couple of sampled points beforeand after each of these multipath components. It will extractinformation and generate various control signals. These control signalscould include the ones to adjust the position of a multipath componentand replace a weak component with a stronger component. The signalcombiner 255 will combine all the significant components together.

[0048]FIG. 3 shows the second embodiment of a dynamic matched filterbank in a communication system.

[0049] Here are some assumptions. First, the multipath fading spans overless than L symbol periods. Second, the M output signals from signalregister or from block reference signal generator correspond to a symbolperiod. Third, the section of a reference signal in any symbol period isdifferent from the section in any other adjacent L symbol periods.

[0050] Being same as the signal register in FIG. 1, signal register 305has M tapped output signals with each one is a replica of the inputsignal S_(in) with different delay.

[0051] There are M output signals from the block reference signalgenerator 310. These M signals are a sampled version of a localreference signal in a symbol period. Since the reference signal changeswith the time, these M signals also change from one symbol period toanother but are constant during a symbol period. When the referencesignal is a PN sequence, the block reference signal is a window of Mchips of the PN sequence with the window moving M chips at the end ofevery M chip clocks or one symbol period.

[0052] The M signals from the block reference signal generator 310 aresent to a register array 315 ₂ and a matched filter 325 ₁. There are L−1register arrays 315 ₂ to 315 _(L) in cascade and L matched filters 325 ₁to 325 _(L). These L matched filters 325 ₁ to 325 _(L) comprise amatched filter bank.

[0053] Like a register array in FIG. 2, each register array has M memoryelements. Each of these memory elements will delay its input signal byexact one symbol period.

[0054] Each matched filter also has M multipliers and an adder. Thesemultipliers will multiply each of the M signals from either the blockreference signal generator 310 or one of the L−1 register arrays 315 ₂to 315 _(L) with a corresponding signal from signal register 305. Theadder will then sum all the products together and a correspondingmatched filter will take the summation as its output.

[0055] For a signal consisting of a section of current reference signal,the first matched filter 325 ₁ will detect all of the multipathcomponents of the signal falling into the first symbol period. Thesecond matched filter 325 ₂ will detect all of the multipath componentsof the signal falling into the second symbol period. The No. L matchedfilter 325 _(L) will detect all of the multipath components of thesignal falling into the No. L symbol period.

[0056] The controller 335 will monitor the signals from each matchedfilter as well as from signal combiner 330, extract information, andgenerate various control signals. Under the control of controller 260,the signal combiner 330 will combine all the significant components frommatched filters 325 ₁ to 325 _(L) together.

[0057]FIG. 4 shows the third embodiment of a dynamic matched filter bankin a direct sequence spread spectrum communication system with thereference signal consisting of a spreading signal and a scrambledsignal.

[0058] The assumptions are same as those with FIG. 2.

[0059] The reference signal is a combination of a scrambled signal and aspreading signal. In FIG. 4, a modified input signals is obtained bymodifying the input signal with the spreading signal. And a bank ofmatched filters is used to obtain the correlation values between themodified input signal and each of the scrambled signals with differentdelays.

[0060] The signal register 405 has M tapped output signals with each oneis a replica of the input signal S_(in) with different delay. Thespreading signal generator 410 also has M output signals, whichcorrespond to a symbol period and are a sampled version of the spreadingsignal. The M output signals from spreading signal generator 410 do notchange with the time.

[0061] There is a multiplier array 415 with M multipliers. Eachmultiplier multiplies a signal from signal register 405 with acorresponding signal from spreading signal generator 410. The matchedfilter 430 ₁ to 430 _(L) will take the M products as their input signal.

[0062] The block scrambled signal generator 410 generates M outputsignals. These M signals are a sampled version of the local scrambledsignal in a section corresponding to a symbol period. They do not changewith in any symbol period but may be change from one symbol period toanother. The M signals will be sent to register arrays 425 ₁ to 425_(L).

[0063] There are M memory elements in each of the register arrays 425 ₁to 425 _(L). Each register array will capture the M output signals fromthe block scrambled signal generator 420 and hold them for L symbolperiods, then recapture another the M output signals and hold foranother L symbol periods, and so on. Different register array willcapture M output signals at different symbol period. The M outputs of aregister array will be sent to a corresponding matched filter as itsreference signal.

[0064] There are L matched filters 430 ₁ to 430 _(L), which comprise amatched filter bank. In a matched filter, there are M multipliers and anadder. Each component of the modified input signal from multiplierregister 415 will be multiplied by a corresponding component of itsreference signal. The matched filter will take the summation as itsoutput signal.

[0065] A first section of a transmitted signal, corresponding to onesymbol, will span over less than L symbol periods during transmission.The first matched filter 430 ₁ will detect all the scattered versions ofthe first section stretched over less than L symbol periods. After allthese L symbol periods have passed, the first matched filter 430 ₁ willbe assigned to detect a new symbol. A second section of the transmittedsignal, corresponding to another symbol and immediately after the firstsection, will also span over less than L symbol periods duringtransmission. The second matched filter 430 ₂ will detect all thescattered versions of the second section stretched over less than Lsymbol periods. The scattered versions of the first section and secondsection will overlap L−1 symbol periods. Other matched filters work inthe same way.

[0066] The controller 440 will monitor the signals from each matchedfilter as well as from each signal combiner, extract information, andgenerate various control signals. These control signals could includethe ones to adjust the position of a multipath component and replace aweak component with a stronger component.

[0067] There are L signal combiners 435 ₁to 435 _(L). Under the controlof controller 440, each signal combiner will combine all of thesignificant components of a multipath signal spanned over less than Lsymbol periods from a corresponding matched filter.

[0068]FIG. 5 shows the fourth embodiment of a dynamic matched filterbank in a communication system.

[0069] The assumptions are same as those with FIG. 3.

[0070] Signal register 505 has M tapped output signals with each one isa replica of the input signal S_(in) with different delay.

[0071] There are M output signals from the block reference signalgenerator 410. These M signals correspond to a symbol period and are asampled version of the local reference signal. They do not change duringany symbol period but could change from one symbol period to another.They are fed to a set of register arrays 515 ₁ to 515 _(L).

[0072] There are M memory elements in each of the register arrays 515 ₁to 515 _(L) Each register array will capture the M output signals fromthe block reference signal generator 510 and hold for L symbol periods,then recapture another the M output signals and hold for another Lsymbol periods, and so on. Different register array will capture Moutput signals at different symbol period.

[0073] There are L matched filters 520 ₁ to 520 _(L), which comprise amatched filter bank. As before, in a matched filter, there are Mmultipliers and an adder. Each of the M signals from one of the Lregister arrays is multiplied by the corresponding signal from signalregister 505 and all the products will be added up. A matched filterwill take a corresponding summation as its output signal.

[0074] A first section of a transmitted signal, corresponding to onesymbol, will span over less than L symbol periods during transmission.The first matched filter 520 ₁ will detect all the scattered versions ofthe first section stretched over less than L symbol periods. After allthese L symbol periods have passed, the first matched filter 520 ₁ willbe assigned to detect a new symbol. A second section of the transmittedsignal, corresponding to another symbol and immediately after the firstsection, will also span over less than L symbol periods duringtransmission. The second matched filter 520 ₂ will detect all thescattered versions of the second section stretched over less than Lsymbol periods. The scattered versions of the first section and secondsection will overlap L−1 symbol periods. And so on. A No. L section ofthe transmitted signal, corresponding to another symbol and immediatelyafter the No. L−1 section, will also span over less than L symbolperiods during transmission. The No. L matched filter 520 _(L) willdetect all the scattered versions of the No. L section stretched overless than L symbol periods. The scattered versions of any two adjacentsections will overlap L−1 symbol periods.

[0075] The controller 530 will monitor the signals from each matchedfilter as well as each signal combiner, extract information, andgenerate various control signals.

[0076] There are L signal combiners 525 ₁to ⁵²⁵ _(L). Under the controlof controller 530, each signal combiner will combine all of thesignificant components of a multipath signal spanned over less than Lsymbol periods from a corresponding matched filter together.

[0077]FIG. 6 shows spreading signals for each of multi-channels and ascrambled signal of a multi-channel direct sequence spread spectrumcommunication system.

[0078] There are N spreading signals 605 ₁ to 605 _(N) with one for eachof the N channels. These N spreading signals S₁ to S_(N) are differentfrom each other. In many cases, they are orthogonal. Also in manysystems, the spreading signals S₁ to S_(N) do not change from one symbolperiod to another.

[0079] There is a scrambled signal or PN signal 610. The section of PNsignal in the first symbol period is denoted by PN₁, in the secondsymbol period is denoted by PN₂, and etc. In order to distinguishmultipath components of a signal, the section of a scramble signal inany of the L symbol periods is different from the section in any othersymbol period. Again L is the number that no significant component of amultipath signal will span over more than L symbol periods.

[0080] The transmitter structure corresponding to the signals in FIG. 6is shown in FIG. 7. The information on each channel is first mapped intoa QAM signal respectively by one of the QAM mapping devices 705 ₁ to 705_(N), and then each of the QAM signals is modulated by one of thespreading signals S₁ to S_(N) at one of the corresponding multipliers710 ₁ to 710 _(N). The products from the multipliers 710 ₁ to 710 _(N)are sent to adder 715. The output signal of adder 715 will be furtherscrambled by a scrambled signal PN at multiplier 720.

[0081] In both FIG. 8 and FIG. 9, each reference signal is a combinationof two signals. When the reference signal is the combination of two ormore signals, each signal is called a component reference signal.Further, when a signal is a sequence of binary bits, one can simply callthe signal as a sequence for simplicity.

[0082]FIG. 8 shows a receiver with a set of dynamic matched filter banksin a multi-channel direct sequence spread spectrum communication system.The reference signal consists of the spreading signals and the scrambledsignal as in FIG. 6 and the dynamic matched filter bank is the similarto the one in FIG. 2.

[0083] There are several assumptions. First, the local reference signalsare the combinations of a PN sequence and a corresponding spreadingsignals. Second, the multipath fading spans over less than L symbolperiods. Third, the M output signals either from signal register or fromblock shift PN generator correspond to a symbol period. Fourth, eachspreading signal has only one section, which corresponds to a symbolperiod and does not change with the time. Fifth, a section of the PNsequence is different from any other section in adjacent L symbolperiods. Sixth, there are N channels with corresponding spreadingsignals S₁ to S_(N).

[0084] For easy to describe, let L=2.

[0085] A group of modified input signals for matched filters areobtained by multiplying the input signal with various copies of the PNsignal with different delays.

[0086] One can separate the devices into two sets of devices. The firstset of devices consists of the block shift PN generator 810, abinary-to-value mapping device 825 ₁, a multiplier array 830 ₁, and thefirst matched filter bank consisting of N matched filters 840 ₁ ⁽¹⁾ to840 _(N) ⁽¹⁾. Together with signal combiner and controller, the firstset of devices are used to detect, track, and combine all of thecomponents of a multipath signal, which fall into a symbol period calledthe first symbol interval. The second set of devices consists of aregister array 815, a binary-to-value mapping device 825 ₂, a multiplierarray 830 ₂, and the second matched filter bank consisting of N matchedfilters 840 ₁ ⁽²⁾ to 840 _(N) ⁽²⁾. Together with signal combiner andcontroller, the second set of devices are used to detect, track, andcombine all of the components of a multipath signal, which fall into thesymbol period immediately after first symbol interval.

[0087] The input signal, S_(in), is shifted into signal register 805.There are M output signals from signal register 805, with each signalbeing a replica of input signal S_(in) with different delay.

[0088] Now let's say how the first set of devices work.

[0089] The block shift PN generator 810 updates its output at the end ofevery M chips. One can build a block shift PN generator by a linearfeedback shift register with feedback logic based on shifting M chips atone time.

[0090] The M binary chips from the block shift PN generator 810 aremapped into proper values by binary-to-value mapping device 825, such asmapping binary 0 to value 1.0 and binary 1 to −1.0.

[0091] The multiplier array 830 ₁ has M multipliers 835 ₁ to 835 _(M).Each of these M values from mapping device 825 ₁ is multiplied by acorresponding signal from signal register 805 at one of the multipliers835 ₁ to 835 _(M).

[0092] Each matched filter consists of M multipliers and an adder. The Mproducts from a multiplier array 830 ₁ will be sent to the matchedfilter 840 ₁ ⁽¹⁾. Each of the multipliers 845 ₁ to 845 _(M) willmultiply one of the M signals from multiplier array 830 ₁ with acorresponding signal of a spreading signal S₁. The adder 850 will addall the products together. The matched filter 840 ₁ ⁽¹⁾ takes thesummation as its output.

[0093] The second set of devices has the similar function as the firstset. The M output signals from block shift PN generator 810 are also fedto a register array 815. In the register array, there are M memoryelements, each of them delays its input by a symbol period, or M chips.The rest devices in second set work in the same way as the correspondingdevices in the first set.

[0094] There are N signal combiners with one for each channel. Eachsignal combiner takes two inputs, one from a corresponding matchedfilter in the first set and another from a corresponding matched filterin the second set. For example, signal combiner 855 ₁ takes the outputsfrom matched filters 840 ₁ ⁽¹⁾ and 840 ₁ ⁽²⁾ to carry out signalcombining.

[0095] The controller 860 will take the outputs from all matched filtersand from all signal combiners to find the information about thecomponents of a multipath signal and generate various control signals.

[0096] There are some relations among these 2N matched filters. First,all the matched filters in the first set have the same input signals,while all the matched filters in the second set have the same inputsignals. Second, in many systems, the spreading signals S₁ to S_(N) areorthogonal, such as Walsh codes. Third, for each matched filter in thefirst set having a particular reference signal, there is a matchedfilter in the second set having the same reference signal. A lot ofhardware could be saved if one build all these matched filters jointlyinstead of treating them as totally independent filters.

[0097]FIG. 9 shows a receiver with a set of dynamic matched filter banksin a multi-channel direct sequence spread spectrum communication system.The reference signal consists of the spreading signals and the scrambledsignal as in FIG. 6 and the dynamic matched filter bank is the similarto the one in FIG. 3.

[0098] There are several assumptions. First, the local reference signalsare the exclusive-or of a PN sequence with each of spreading sequences.Second, the multipath fading spans over less than L symbol periods.Third, the M output signals either from signal register or from blockshift PN generator correspond to a symbol period. Fourth, each spreadingsequence has only one section, which corresponds to a symbol period anddoes not change with the time. Fifth, the section of a PN sequence inany symbol period is different from any other the section in adjacent Lsymbol periods. Sixth, there are N channels with corresponding spreadingsequences S₁ to S_(N).

[0099] For easy to describe, let L=2.

[0100] Essentially the system in FIG. 9 is the same as the system inFIG. 8. The difference is due to the change of operation order.

[0101] Also there are two set of devices. Together with signal combinerand controller, the first set of device is trying to detect and trackthe multipath signals falling into the first symbol period and thesecond is trying to detect and track the multipath signals falling intothe second symbol period. The first set consists of a block shift PNgenerator 910, N exclusive-or array 920 ₁ ⁽¹⁾ to 920 _(N) ⁽¹⁾,binary-to-value mapping device 930 ₁ ⁽¹⁾ to 930 _(N) ⁽¹⁾, the firstmatched filter bank consisting of N matched filters 935 ₁ ⁽¹⁾ to 935_(N) ⁽¹⁾. The second set consists of a register array 915, Nexclusive-or array 920 ₁ ⁽²⁾ to 920 _(N) ⁽²⁾, N binary-to-value mappingdevice 930 ₁ ⁽²⁾ to 930 _(N) ⁽²⁾, and the second matched filter bankconsisting of N matched filters 935 ₁ ⁽²⁾ to 935 _(N) ⁽²⁾. In each set,there are N subsets with each subset consisting of an exclusive-orarray, a binary-to-value mapping device, and a matched filter. Eachsubset works exactly in the same way.

[0102] The input signal, S_(in), is shifted into signal register 905.There are M output signals from signal register 905, with each signalbeing a replica of input signal S_(in) with different delay.

[0103] The block shift PN generator 910 is just like a regular PNgenerator except the feedback logic is based on shifting M chips at theend of every M chip clock cycles instead of shifting 1 chip at end ofevery chip clock cycle.

[0104] The register array 915, coupled to block shift PN generator 910,has M memory units to store M chips. It also delays its input by onesymbol period or M chips.

[0105] Let's look at the subset containing the matched filter 935 ₁ ⁽¹⁾.

[0106] The block of M chips generated by block shift PN generator 910 isfed into a exclusive-or array 920 ₁ ⁽¹⁾, where each of M chips isexclusive-or with a corresponding chip of the spreading signal S₁respectively by one of the exclusive-or gate 925 ₁ to 925 _(M). These Mchips are converted into M values by a binary-to-value mapping device930 ₁ ⁽¹⁾. One way of mapping is to map binary 0 to value 1.0 and binary1 to value −1.0. The M values from the output binary-to-value mappingdevice 930 ₁ ⁽¹⁾ is sent to matched filter 935 ₁ ⁽¹⁾ as its referencesignal.

[0107] Matched filter 935 ₁ ⁽¹⁾ consists of M multipliers and an adder.Each of the M values is multiplied by a corresponding signal from signalregister 905 respectively at one of the multipliers. The products fromthese multipliers will be added together by the adder.

[0108] For each channel, there is a signal combiner. Each signalcombiner takes two inputs, one from a corresponding matched filter inthe first set and one from a corresponding matched filter in the secondset. For example, for channel one, the signal combiner 950 ₁ takes twoinputs, one from the matched filter 935 ₁ ⁽¹⁾ of the first set andanother from the matched filter 935 ₁ ⁽²⁾ of the second set. The signalcombiner 950 ₁ will combine the two inputs together.

[0109] All the outputs from various matched filters 935 ₁ ⁽¹⁾ to 935_(N) ⁽¹⁾ and from 935 ₁ ⁽²⁾ to 935 _(N) ⁽²⁾ as well as from signalcombiners 950 ₁ to 950 _(N) will sent to controller 955. The controller955 will extract information, find and update multipath information, andgenerate various controlling signals.

[0110] There are also some relations among these 2N matched filters. Alot of hardware could be saved if one build all these matched filtersjointly instead of treating them as totally independent filters.

What is claimed is:
 1. A subsystem for detecting, tracking, andcombining the components of a multipath fading signal spanned overseveral symbol periods, comprising: a signal register, receiving a inputsignal, for generating a section of the input signal, which is a movingsection of sampled version of the input signal with the delay betweenany two adjacent samples being equal; a block reference signal generatorfor generating a section of a reference signal and holding the sectionfor a certain amount of time, then generating another section of thereference signal, with the second section being immediately after thefirst section and the lengths of two sections being equal, and holdingthe new section for same amount of time, and repeating the process; anda plurality of matched filters, wherein each matched filter is forfinding the correlation between a section of the input signal and asection of the matched-filter specific reference signal for the matchedfilter.
 2. A subsystem for detecting, tracking, and combining thecomponents of a multipath fading signal spanned over several symbolperiods as in claim 1, wherein a section of a reference signal is a setof sampled values of the reference signal in one symbol period andwherein a certain amount of time is one symbol interval.
 3. A subsystemfor detecting, tracking, and combining the components of a multipathfading signal spanned over several symbol periods as in claim 1, whereina section of the matched-filter specific reference signal for thematched filter is a section of the signal selected from the groupconsisting of the reference signal and its varied versions with one toplurality symbol delays.
 4. A subsystem for detecting, tracking, andcombining the components of a multipath fading signal spanned overseveral symbol periods as in claim 1, wherein a block reference signalgenerator is a linear feedback shift register with a feedback logic toshift a plurality of chips at one time.
 5. A subsystem for detecting,tracking, and combining the components of a multipath fading signalspanned over several symbol periods as in claim 1, further comprising aplurality of register arrays, one of which is coupled to the blockreference signal generator with each of the rest coupled to its previousregister array, wherein each register array is for delaying the sectionof the signal at its input by a symbol period and providing acorresponding matched filter a section of the matched-filter specificreference signal.
 6. A subsystem for detecting, tracking, and combiningthe components of a multipath fading signal spanned over several symbolperiods as in claim 5, further comprising: a controller, receivingsignals from all the matched filters and all the signal combiners, forextracting and generating various control signals; and a plurality ofsignal combiners, wherein a respective signal combiner is coupled to aplurality of matched filters, each signal combiner for combining thecomponents of a multipath signal.
 7. A subsystem for detecting,tracking, and combining the components of a multipath fading signalspanned over several symbol periods as in claim 1, further comprising aplurality of register arrays, each of which is coupled to the blockreference signal generator, wherein each register array is for capturingthe section of the reference signal at different time, holding thesection by a plurality of symbol periods, and providing a correspondingmatched filter a section of the matched-filter specific referencesignal.
 8. A subsystem for detecting, tracking, and combining thecomponents of a multipath fading signal spanned over several symbolperiods as in claim 7, further comprising: a controller, receivingsignals from all the matched filters and all the signal combiners, forextracting information and generating various control signals; and aplurality of signal combiners, wherein a respective signal combiner iscoupled to a corresponding matched filter, each signal combiner forcombining the components of a multipath signal.
 9. A subsystem fordetecting, tracking, and combining the components of a multipath fadingsignal spanned over several symbol periods, comprising: a signalregister, receiving a input signal, for generating a section of theinput signal, which is a moving section of sampled version of the inputsignal with the delay between any two adjacent samples being equal; afirst component reference signal generator for generating a section of afirst component reference signal and holding the section for a certainamount of time, then generating another section of the first componentreference signal, with the second section being immediately after thefirst section and the lengths of two sections being equal, and holdingthe new section for same amount of time, and repeating the process; asecond component reference signal generator for generating a section ofa second component reference signal; and a plurality of matched filters,wherein each matched filter is for finding the correlation between asection of the matched-filter specific input signal to the matchedfilter and a section of the matched-filter specific reference signal forthe matched filter.
 10. A subsystem for detecting, tracking, andcombining the components of a multipath fading signal spanned overseveral symbol periods as in claim 9, wherein a section of a firstcomponent reference signal is a set of sampled values of the firstcomponent reference signal in one symbol period and wherein a certainamount of time is one symbol interval.
 11. A subsystem for detecting,tracking, and combining the components of a multipath fading signalspanned over several symbol periods as in claim 9, wherein a firstcomponent reference signal generator is a linear feedback shift registerwith a feedback logic to shift a plurality of chips at one time.
 12. Asubsystem for detecting, tracking, and combining the components of amultipath fading signal spanned over several symbol periods as in claim9, wherein a section of the matched-filter specific reference signal forthe matched filter is a section of the second component referencesignal.
 13. A subsystem for detecting, tracking, and combining thecomponents of a multipath fading signal spanned over several symbolperiods as in claim 12, further comprising: a plurality of registerarrays, one of which is coupled to the first component reference signalgenerator with each of the rest coupled to its previous register array,wherein each register array is for delaying the section of the signal atits input by a symbol period; and a plurality of multiplier arrays, oneof which is coupled to the first component reference signal generatorwith each of the rest coupled to its corresponding register array,wherein each multiplier array is for multiplying a section of the inputsignal by a section of signal from a device selected from the groupconsisting of the first component reference signal generator and aplurality of register arrays and providing a corresponding matchedfilter a section of the matched-filter specific input signal.
 14. Asubsystem for detecting, tracking, and combining the components of amultipath fading signal spanned over several symbol periods as in claim9, further comprising: a plurality of register arrays, each of which iscoupled to the first component reference signal generator, wherein eachregister array is for capturing a section of the first componentreference signal at different time, holding the section by a sameplurality of symbol periods, and providing a corresponding matchedfilter a section of the matched-filter specific reference signal; and amultiplier array, coupled to the second component reference signalgenerator, is for multiplying a section of the input signal by a sectionof the second component reference signal and providing each matchedfilter a section of the matched-filter specific input signal.
 15. Asubsystem for detecting, tracking, and combining the components of amultipath fading signal spanned over several symbol periods in a radiolink of a multi-channel spread spectrum communication system,comprising: a signal register, receiving an input signal, for generatinga moving section of the sampled version of input signal; a firstcomponent reference signal generator, with a feedback logic based onshifting a block of chips at end of each symbol period, for generating asection of a first component reference signal and holding the sectionfor one symbol period, then generating another section of the firstcomponent reference signal, with the second section being immediatelyafter the first section and the lengths of two sections being equal, andholding the new section for one symbol period, and repeating theprocess; a plurality of register arrays, one of which is coupled to thefirst component reference signal generator with each of the rest coupledto its previous register array, wherein each register array is forcapturing the section of the signal at its input and holding the sectionfor one symbol period, then capturing another section of the signal atits input and holding the new section for symbol period, and so on; aplurality of second component reference signal generators, wherein arespective second component reference signal generator for generating aspreading signal to spread the information on a corresponding channel; aplurality of matched filters, wherein a respective matched filter forfinding the correlation between a section of the matched-filter specificinput signal to the matched filter and a section of the matched-filterspecific reference signal for the matched filter; a plurality of signalcombiners, wherein a respective signal combiner is coupled to thecorresponding matched filters, each signal combiner for combining thecomponents of a multipath signal together; and a controller, receivingsignals from all the matched filters and all the signal combiners, forextracting information and generating various control signals.
 16. Asubsystem for detecting, tracking, and combining the components of amultipath fading signal spanned over several symbol periods in a radiolink of a multi-channel spread spectrum communication system as in claim15, wherein a section of the matched-filter specific reference signalfor the matched filter is a section of signal from a correspondingsecond component reference signal generator.
 17. A subsystem fordetecting, tracking, and combining the components of a multipath fadingsignal spanned over several symbol periods in a radio link of amulti-channel spread spectrum communication system as in claim 16,further comprising a plurality of multiplier arrays, one of which iscoupled to the first component reference signal generator with each ofthe rest coupled to its corresponding register array, wherein eachmultiplier array is for multiplying a section of the input signal by asection of the signal from a device selected from the group consistingof the first component reference signal generator and a plurality ofregister arrays and providing a corresponding matched filter a sectionof the matched-filter specific input signal.
 18. A subsystem fordetecting, tracking, and combining the components of a multipath fadingsignal spanned over several symbol periods in a radio link of amulti-channel spread spectrum communication system as in claim 15,wherein a section of the matched-filter specific input signal to thematched filter is a section of the input signal.
 19. A subsystem fordetecting, tracking, and combining the components of a multipath fadingsignal spanned over several symbol periods in a radio link of amulti-channel spread spectrum communication system as in claim 18,further comprising a plurality of exclusive-or arrays, one of which iscoupled to the first component reference signal generator with each ofthe rest coupled to its corresponding register array, wherein eachexclusive-or array is for exclusive-oring a section of the signal from adevice selected from the group consisting of the first componentreference signal generator and a plurality of register arrays with asection of the signal from a corresponding second component referencesignal generator and providing a corresponding matched filter a sectionof the matched-filter specific reference signal.